Pacing leads with a structured coating

ABSTRACT

An implantable medical device includes a lead body having a distal end and a proximal end, a lumen and at least one lead wire extending through the lumen. The lead wire has an outer surface and a polymeric coating on at least a portion of the outer surface of the lead wire. The coating includes a first structure having a first end proximate the outer surface of the lead wire and a second end opposite the first end. The second end is movable relative to the first end and relative to the lead wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) to U.S.Provisional Application 61/773,471, entitled “PACING LEADS WITH ASTRUCTURED COATING”, filed on Mar. 6, 2013, which is herein incorporatedby reference in its entirety.

TECHNICAL FIELD

The present invention relates to a medical device having a coating, andmore particularly, to a medical device having a coating containingmicrostructures for reducing wear. Methods of making such coatings arealso provided.

BACKGROUND

A lead includes one or more lead wires extending through a lead body.The lead wires may be metallic while the lead body may be a silicone orpolyurethane material. The lead body isolates the lead wires fromsurrounding tissue and any external environment that could compromisethe lead's performance.

During use, lead wires may rub on the inner surface of the lead body dueto the constant movement of the patient. Over time, the lead wires mayabrade or wear on the inner surface of the lead body. In somecircumstances, such wear can result in a failure of the isolation systemand short-circuiting of the lead.

SUMMARY

Disclosed herein are various embodiments of a coated medical device, aswell as methods for coating medical devices.

In Example 1, an implantable medical device includes a lead body havinga distal end and a proximal end, a lumen extending through the lead bodyfrom the distal end to the proximal end and at least one lead wireextending through the lumen from the distal end to the proximal end. Thelead wire has an outer surface and a polymeric coating on at least aportion of the outer surface of the lead wire. The polymeric coatingcomprises a plurality of flexible microstructures extending outwardlyfrom a surface of the polymeric coating.

In Example 2, the implantable medical device according to Example 1 andfurther including a second lumen extending through the lead body and asecond lead wire extending through the second lumen. A second polymericcoating is on at least a portion of the second lead wire and includes aplurality of flexible microstructures extending outwardly from a surfaceof the second polymeric coating.

In Example 3, the implantable medical device 1 according to Example 1 orExample 2, wherein the distance from a first end and a second end of themicrostructure is from 5 micrometers to 100 micrometers.

In Example 4, the implantable medical device according to any ofExamples 1-3, wherein the coating includes at least one of ethylenetetrafluoroethylene (ETFE) and polyethylene terephthalate (PET).

In Example 5, the implantable medical device according to any ofExamples 1-4, and further including a protective coating on at least aportion of the flexible microstructures.

In Example 6, the implantable medical device according to Example 5,wherein the protective coating has a thickness of 3 nanometers to 30nanometers.

In Example 7, the implantable medical device according to Example 5 orExample 6, wherein the protective coating has a higher modulus ofelasticity than the polymeric coating.

In Example 8, the implantable medical device according to any ofExamples 1-7, and further including a lubricant between at least aportion of an inner surface of the lead body and at least a portion ofthe microstructures.

In Example 9, an implantable medical device includes a lead body, atleast one lead wire and a polymeric coating. The lead body has a distalend and a proximal end and includes at least one lumen and at least oneinner surface extending from the distal end to the proximal end. Thelead wire extends through the lumen and has an outer surface. Thepolymeric coating is disposed on at least a portion of the outer surfaceof the lead wire. The polymeric coating includes a plurality of flexiblemicrostructures that extend outwardly from the outer surface of the leadwire and that have at least one point of contact with the inner surfaceof the lead body.

In Example 10, the implantable medical device according to Example 9,wherein the microstructures are integral with the polymeric coating.

In Example 11, the implantable medical device according to eitherExample 9 or 10, wherein the microstructures can bend at least 0.0015radians.

In Example 12, the implantable medical device according to any ofExamples 9-11, wherein the microstructures have a minimum diameter and alength that is at least twice the minimum diameter.

In Example 13, a method of forming an implantable medical deviceincludes forming a polymeric coating on an outer surface of a lead wire,and treating the coating to form a plurality of flexible microstructuresextending outward from a surface of the coating.

In Example 14, the method according to Example 13, wherein treating thecoating includes laser treating the coating.

In Example 15, the method according to Example 13, wherein treating thecoating includes treating the coating with carbon dioxide.

In Example 16, the method according to any of Examples 13-15, whereinforming the polymeric coating includes forming a polymeric coatinghaving a thickness from 5 micrometers to 100 micrometers.

In Example 17, the method according to any of Examples 13-16, andfurther comprising applying a protective coating on at least a portionof the flexible microstructures.

In Example 18, the method according to Example 17, wherein applying theprotective coating includes applying at least one layer including apolymeric material and applying at least one layer including a ceramicmaterial, wherein the layer including the ceramic material has athickness of about 30 nanometers or less.

In Example 19, the method according to any of Examples 13-18, andfurther including positioning the lead wire having the plurality ofmicrostructures within a lumen of a lead body and wherein the polymericcoating has a higher modulus of elasticity than the lead body.

In Example 20, the method according Example 19, and further includingdispensing a lubricant between the microstructures and the lead body.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of an implantable device.

FIG. 2A illustrates an exemplary cross-sectional view of the implantabledevice of FIG. 1.

FIG. 2B illustrates an alternative exemplary cross-sectional view of theimplantable device of FIG. 1.

FIG. 3 is a schematic of an exemplary coating.

FIG. 4A and FIG. 4B are schematics of alternative exemplary coatings.

FIG. 5 is an exemplary method for forming an exemplary coating.

FIG. 6 is a scanning electron microscope image of laser induced periodicsurface structures.

While the invention is amenable to various modifications and alternativeforms, specific embodiments have been shown by way of example in thedrawings and are described in detail below. The intention, however, isnot to limit the invention to the particular embodiments described. Onthe contrary, the invention is intended to cover all modifications,equivalents, and alternatives falling within the scope of the inventionas defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 illustrates an implantable device 100, such as a lead 102 for usewith a pulse generator 105. Implantable device 100 includes a lead body110, and at least one elongate conductor 120 contained within the leadbody 110. The lead body 110 extends from a proximal end 112 to a distalend 114. The proximal end 112 of the lead 102 is electrically coupledwith the pulse generator 105, for example, with a terminal pin 131.

The implantable device 100 generically represents, but is not limitedto, cardiac function management (referred to as “CFM”) systems such aspacers, cardioverters/defibrillators, pacers/defibrillators,biventricular or other multi-site resynchronization or coordinationdevices such as cardiac resynchronization therapy (referred to as “CRT”)devices, sensing instruments, drug delivery systems, neurostimulationdevices, or organ stimulation devices. Thus, the implantable device 100can be utilized for any application that delivers a product, such as anelectrical shock or pulse or a drug.

The optional pulse generator 105 includes a source of power as well aselectronic circuitry (not shown). In some embodiments, the electroniccircuitry can include one or more microprocessors that provideprocessing and/or evaluation functions, and that can determine anddeliver electrical shocks or pulses of different energy levels andtiming. The pulse generator can be employed as part of a variety ofuseful therapies, including for neurostimulation or ventriculardefibrillation or cardioversion. It can also be used to pace the heartin response to one or more sensed cardiac arrhythmia includingfibrillation, cardiac resynchronization, tachycardia, or bradycardia. Insome embodiments, the pulse generator 105 can be powered by one or morebatteries, though any other internal or external power source may beused for the given application. In some embodiments, the pulse generator105 can sense intrinsic signals of the heart and generate a series oftimed electrical discharges.

The implantable device 100 may further include one or more electrodes115. The one or more electrodes 115 are each electrically coupled withthe at least one conductor 120. The electrode 115 allows for electricalsignals to be delivered from the pulse generator 105 to the targettissue or location.

The implantable device 100 can include one or more features that enablethe lead body 110 to be secured or fixed within a patient. For example,the lead body 110 can include passive fixation features, such as one ormore tines and/or an active fixation assembly, such as a fixation helix.

The lead body 110 is designed to separate and isolate electricallyconductive components within the lead body 110 from surrounding tissuesof the patient. Even under ordinary and expected conditions, onceimplanted the conductive components can rub against and wear the innersurface of the lead body 110. Over time, this repeated wearing canresult in failure of the isolation, which in turn can result in shortcircuiting. In some embodiments described herein, the electricallyconductive components include a coating which may reduce wear.

FIG. 2A illustrates a cross-sectional view of an embodiment of animplantable device 100 which includes a lead body 110 (having an outersurface 122, an inner surface 124, and a lumen 126), a lead wire 128having an outer surface 130, and a polymeric coating 132. Although thepolymeric coating 132 is illustrated schematically as having a smoothsurface, the polymer coating 132 may include a plurality ofmicrostructures which extend generally outward from a surface of thepolymer coating 132 towards the inner surface 124 of the lead body 110.

The lead body 110 is generally flexible, but substantiallynon-compressible along its length. The lead body 110 may have anysuitable cross-sectional shape. For example, in some embodiments, thelead body 110 may have a substantially circular cross-section. The leadbody 110 may be of any suitable size for implantation. In someembodiments, the lead body 110 may have a substantially circularcross-section and the outer diameter of the lead body 110 may rangebetween about 0.6 millimeters (mm) and about 5 mm.

The lead body 110 can isolate the lead wire 128 from the surroundingtissue or environment. The lead body 110 may include a suitablebio-compatible, electronically insulative material. For example, in someembodiments, the lead body 110 may include silicone or a polyurethane.In some embodiments, the lead body 110 may have a substantially uniformcomposition along its length. In other embodiments, the composition ofthe lead body 110 may vary in any direction, including along the lengthand/or thickness.

The lead body 110 can include one or more channels or lumens 126extending axially through the lead body 110 from the proximal end to thedistal end of the lead body 110. The lumen 126 forms the inner surface124 of the lead body 110. The lumen 126 can have any suitablecross-sectional shape, such as a substantially circular, rectangular, ortriangular cross-sectional shape. The lumen 126 can have a substantiallyuniform cross-sectional area or the cross-sectional area may vary alongthe length of the lumen 126 (or the lead body 110).

One or more lead wires 128 can extend through the one or more lumens126. In some embodiments, the lead wire 128 may extend from the proximalend to the distal end of the lead body 110. For example, the lead wire128 may be parallel with a longitudinal axis of the lead body 110.

The lead wire 128 is conductive and may include any suitable conductivematerial. For example, in some embodiments, the lead wire 128 may bemetallic.

The polymeric coating 132 may completely surround or may cover anyportion of the outer surface 130 of the lead wire 128. The polymericcoating 132 is positioned between the outer surface 130 of the lead wire128 and the inner surface 124 of the lead body 110. As described herein,the polymeric coating 132 may decrease friction between the lead wire128 and the inner surface 124. Additionally or alternatively, thepolymeric coating 132 may reduce wear on the inner surface 124 of thelead body 110.

Suitable materials for the polymeric coating 132 include materials thatreduce the wear on the lead body 110. For example, suitable polymericmaterials for the polymeric coating 132 may include rubber (natural,butyl, silicone), polyamides such as nylon, polyesters such as Mylar,polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC),polymethylmethacrylate (PMMA), polycarbonate (PC),polytetrafluoroethylene (PTFE), polyethylenes (PE) such as low-densityPE (LDPE), medium-density PE (MDPE), high-density PE (HDPE), andcross-linked PE (XLPE), ethylene tetrafluoroethylene (ETFE) andpolyethylene terephthalate (PET). In some embodiments, the polymericcoating 132 may have a higher modulus of elasticity than the lead body110, e.g., the polymeric coating 132 may be made of a material that isharder than that of the lead body 110.

FIG. 2B is an alternative cross-sectional view in which lead body 110′includes multiple (e.g., three) lumens 126′. One or more lead wires 128′can extend through each lumen 126′ and a polymeric coating 132′ cancover all or a portion of each of the lead wires 128′. The lead body110′, lumens 126′ and polymeric coating 132′ may be substantiallysimilar to those described with respect to FIG. 2A.

FIG. 3 is a schematic drawing of an exemplary polymeric coating 132 onthe outer surface 130 of the lead wire 128 and including bulk or basematerial 134 and one or more microstructures or hairs 136 having firstor bulk ends 138 and second or tip ends 140. The bulk material 134 maybe directly adjacent to the outer surface 130 of the lead wire 128.Alternatively, one or more intermediary materials or layers may bepositioned between the polymeric coating 132 and the outer surface 130of the lead wire 128.

The microstructures 136 may be three-dimensional objects that generallyextend outwardly from the polymeric coating 132 (and indirectly from theouter surface 130 of the lead wire 128.) In some embodiments, themicrostructures 136 may resemble “pillars” or “hairs” extending from thebulk 134 of the polymeric coating 132 on the lead wire 128.

The bulk ends 138 of the microstructures 136 may be adjacent the bulkmaterial 134 and the tip ends 140 may be opposite the bulk ends 138. Forexample, the bulk ends 138 may be closer to the outer surface 130 of thelead wire 128 than the tip ends 140.

In some embodiments, the microstructures 136 and the bulk material 134may have a unitary construction. For example, the microstructures 136and the bulk material 134 can be integral. Alternatively, themicrostructures 136 and the bulk material may be separate structures.

The location of the microstructures 136 on the bulk material 134 may berandom or may form a pattern or an array. For example, themicrostructures 136 may be positioned in a random pattern by treatingthe polymeric material 132 with a laser. In some embodiments, themaximum cross-sectional area of the connecting area between the bulkmaterial 134 and the microstructures 136 is smaller than about 1/10^(th)of the total surface area of the microstructures 136. That is, in someembodiments, the maximum cross-sectional area of the bulk ends 138 whichconnect the microstructures 136 to the bulk material 134 may be lessthan about 1/10^(th) of the total surface area of the microstructures136.

The microstructures 136 may have any number of cross-sectional shapes,where cross-section refers to a cross-section taken generally parallelto the bulk material 134 of the polymeric coating 132. For example, themicrostructures 136 may have a generally rectangular or triangularcross-sectional shape. In some embodiments, the microstructures 136 mayhave a generally circular cross-sectional shape, which may enable themicrostructures 136 to bend in all directions perpendicular to thesurface of the bulk material 134.

The microstructures 136 may have a substantially uniform cross-sectionalarea along the length or the cross-sectional area may vary along thelength of the microstructures 136. For example, the cross-sectional areaof a microstructure 136 may increase and then decrease along aperpendicular vector away from a surface of the polymeric coating 132(e.g., a surface of bulk material 134) thereby creating a bulge. Thebulge may be at the tip end 140 and/or at a location between the bulkend 138 and the tip end 140.

The microstructures 136 may have a maximum cross-sectional thickness ordiameter from about 5 micrometers (um) to about 50 um, from about 5 umto about 25 um, from about 5 um to about 20 um or from about 5 um toabout 15 um.

The microstructures 136 may also have a minimum cross-sectionalthickness or diameter, which may be the same or different than themaximum cross-sectional thickness or diameter. Suitable minimumcross-sectional thicknesses or diameters for the microstructures 136 maybe from about 2.5 um to about 50 um, from about 5 um to about 25 um orfrom about 5 um to about 10 um.

The length or height of a microstructure 136 can be measured from thebulk end 138 to the tip end 140. In some embodiments, themicrostructures 136 can be any suitable length that serves to reducefriction between the lead wire 128 and the lead body 110. Additionally,the length of the structures can be any suitable length that maintainsthe lead body 110 within a useful thickness or diameter. In someembodiments, the length of a microstructure 136 may be at least twice aslong as the minimum diameter or thickness of the microstructure 136.

In some embodiments, the length of the microstructures 136 can be on themicrometer scale. For example, the length of the microstructures 136 canrange between about 5 um and about 100 um. Alternatively, themicrostructures 136 can have a length of about 10 um to about 50 um. Ina still further alternative, the microstructures 136 can have a lengthof about 20 um to about 30 um.

In some embodiments, the microstructures 136 may be elastic or flexible.For example, the microstructures 136 may individually bend, flex or movesimilar to the bristles of a toothbrush. The ability or degree to whichthe microstructures 136 can bend depends on, among other factors, thepolymeric material of the microstructures 136 and/or the thickness ordiameter of the microstructures 136. In some embodiments, themicrostructures 136 may be spaced so that the microstructures 136 canbend a minimum of 0.0015 radians without touching an adjacentmicrostructure 136.

In some embodiments, the lead wire 128 including the polymeric coating132 having the microstructures 136 may be positioned within the leadbody 110, and the microstructures 136 may extend outwardly from the bulkmaterial 134 towards the inner surface 124 of the lead body 110. In someembodiments, the microstructures 136 may contact the inner surface 124of the lead body 110, and the microstructures 136 may individually bendor move during such contact. For example, the lead wire 128 includingthe polymeric coating 132 having the microstructures 136 may bepositioned within the lead body 110 such that at least one of themicrostructures 136 extends outwardly from the bulk material 134 (andindirectly from the lead wire 128) and has at least one point of contactwith the inner surface 124 of the lead body 110.

While not wishing to be bound by any particular theory, it is believedthat the microstructures 136 of the polymeric coating 132 may reduce thewear or abrasion caused by the lead wire 128 on the lead body 110. Forexample, the flexibility of the microstructures 136 may reduce thefriction created between the lead wire 128 and the lead body 110, thusreducing wear on the inner surface 124 of the lead body 110. Themicrostructures 136 may also have a reduced contact surface area withthe inner surface 124 as compared to the contact surface area betweenthe lead wire 128 without the polymeric coating 132 and the innersurface 124, which may also reduce wear on the inner surface 124.

As shown in FIG. 4A, in some embodiments, a protective coating 142 maycover all or at least a portion of polymeric coating 132. In someembodiments, the protective coating 142 may have a higher modulus ofelasticity than the polymeric coating 132. That is, the polymericcoating 132 may be more flexible than the protective coating 142.Additionally or alternatively, the protective coating 142 may be moreresistive to wear from contact with the inner surface 124 as compared tothe polymeric coating 132.

In some embodiments, the microstructures 136 including the protectivecoating 142 are flexible. That is, in some embodiments, themicrostructures 136 including the protective coating 142 can bend, flexor move when they contact the inner surface 124 of the lead body 110.The ability or degree to which the microstructures 136 can flex dependson the thickness and material of the polymeric coating 132 and theprotective coating 142, among other factors.

The protective coating 142 may protect the microstructures 136 when themicrostructures 136 contact the inner surface 124 of the lead body 110.For example, the protective coating 142 may reduce the likelihood thatthe microstructures 136 are damaged or break during contact with thelead body 110. In some embodiments, the protective coating 142 mayprotect the microstructures 136 from damage due, at least in part, tothe higher modulus of elasticity of the protective coating 142.

Additionally, the protective coating 142 may fill defects or cracks,such as micro- or nano-size cracks, in the polymeric coating 132, whichotherwise could be an originating location for larger cracks and damageto the polymeric coating 132.

Suitable materials for protective coating 142 may include a ceramic or apolymeric material. In certain embodiments, suitable materials for theprotective coating 142 include polyamides. In other embodiments,suitable materials for the protective coating include aluminum oxide andpolyurethanes.

In some embodiments, the protective coating 142 may have a thicknessthat reduces damage experienced by the microstructures 136 duringcontact with lead body 110 while still enabling the microstructures 136to be flexible (e.g., to bend, flex or move). In some embodiments, theprotective coating 142 may have a thickness of about 75 nanometers orless. For example, in some embodiments, the protective coating 142 mayhave a thickness of about 5 nanometers (nm) to about 75 nm. In otherembodiments, the protective coating 142 may have a thickness of about 5nm to about 50 nm. In still further embodiments, the protective coating142 may have a thickness of about 5 nm to about 10 nm.

Ceramic layers having a thickness of greater than 30 nm may have anincreased probability of cracking or breaking. When protective coating142 includes a ceramic material, the protective coating 142 may have athickness of about 30 nanometers or less. For example, in someembodiments, the protective coating 142 may have a thickness of about 3nanometers (nm) to about 30 nm. In other embodiments, the protectivecoating 142 may have a thickness of about 5 nm to about 20 nm. In stillfurther embodiments, the protective coating 142 may have a thickness ofabout 5 nm to about 10 nm.

In some embodiments, a lubricant may be present between the innersurface 124 of the lead body 110 and the polymeric coating 132 orprotective coating 142. For example, the lubricant may be dispersed inthe lumen 126.

The lubricant may be any suitable material that reduces friction. Forexample, the lubricant may reduce friction between the inner surface 124of the lead body 110 and the polymeric coating 132 or protective coating142. In some embodiments, suitable lubricants include silicon oil,fluorosilicone oil, and polyethylene glycol (PEG) with a molecularweight less than about 600 g/mol.

The lubricant may further reduce wear on the inner surface 124 of thelead body 110, for example by reducing the friction between the innersurface 124 of the lead body 110 and the polymeric coating 132 orprotective coating 142. In some embodiments, the microstructures 136 mayprovide a porous structure which may retain at least a portion of thelubricant. The microstructures 136 may also assist with maintainingdispersion of the lubricant among the length of the lead body 110 andthe lead wire 128.

In some embodiments, the polymeric coating 132 and/or the protectivecoating 142 may also provide a porous structure which may retain atleast a portion of the lubricant.

FIG. 4B illustrates an alternative, hybrid, protective coating 142 whichincludes two or more layers of different materials. For example, thehybrid protective coating 142 may include two or more layers of ceramicmaterial, two or more layers of polymeric material and/or alternatinglayers of ceramic material and polymeric material. For example, thehybrid protective coating 142 may include a ceramic layer 142 a adjacentto the polymeric coating 132 and a polymeric layer 142 b adjacent theceramic layer 142 a.

The hybrid protective coating 142 may be formed by an atomic layerdeposition process in which the precursors are switched to change thedeposited layer. In some embodiments, ceramic layers having a thicknessgreater than 30 micrometers may have a greater probability of crackingdue at least in part to the low flexibility of ceramic materials.Alternating ceramic and polymeric material embeds the less flexibleceramic material in a flexible polymer layer, and may enable theprotective coating 142 to be greater than about 30 micrometers thick,while the ceramic layer(s) 142 a of the protective coating 142 mayindividually have a thickness of about 30 micrometers or less. Suitableorganic-inorganic combinations for protective coating 142 includepolyamide-polyimide combinations.

An exemplary method 144 for forming the medical device 100 having apolymeric coating 132 including microstructures 136 is illustrated inthe block diagram of FIG. 5, which includes forming a polymeric coatingon a lead wire (block 146), treating the polymeric coating (block 148),optionally applying a protective coating (block 150), positioning thelead wire within a lead body (block 152), and optionally dispensing alubricant between the lead wire and the lead body (block 154).

The polymeric coating may be formed on the lead wire using a variety ofknown techniques (block 146). In one embodiment, the polymeric coatingmay be formed on the lead wire by brush coating, spray coating, or dipcoating, followed by a curing process. In certain embodiments, thepolymeric coating may have a thickness of about 5 um to about 100 um. Inother embodiments, the polymeric coating may have a thickness from about10 um to about 50 um or from about 20 um to about 30 um.

The polymeric coating may be treated to form the microstructures orhairs (block 148). In some embodiments, the microstructures, or hairs,can be formed on the polymeric coating using known techniques. Forexample, the polymeric coating may be treated with a laser treatment. Insome embodiments, the polymeric coating may be exposed to laser energyin order to provide a coating characterized by the microstructuresdescribed herein. The size and shape of the microstructures can becontrolled by selecting the laser parameters such as wavelength,fluence, and exposure time. In some embodiments, a suitable lasertreatment may include polarized pulsed laser irradiation at fluencelevels below the ablation threshold of the polymeric coating, and mayproduce microstructures, which may also be referred to as laser inducedperiodic surface structures (LIPSS). During the polarized pulsed laserirradiation, the polymer is melted very briefly during nano-secondpulses. The electric field (which is in one direction because of thepolarization) causes a small percentage of the polymer dipole segmentsto align themselves with the field during the phase. Repeated laserpulsing gives an incremental effect and can cause the majority of thepolymer dipole segments to align. In certain embodiments, a suitablewavelength of the laser is 196 nm, 356 nm or other conventional laserfrequencies. FIG. 6 is a scanning electron microscope image of exemplaryLIPSS or microstructures.

In other embodiments, the microstructures can be formed on the polymericcoating by use of suitable printing process, such as a compressed carbondioxide assisted nanoimprint lithography technique. For example, a moldmay be placed over the polymeric coated lead wire. The mold may bedepressed using compressed carbon dioxide in a pressure chamber to formflexible microstructures on the surface of the lead wire.

An optional protective coating may be applied to the polymeric coatingafter formation of the microstructures (block 150). As described herein,the protective coating may include a ceramic material, a polymericmaterial or alternating layers of ceramic and polymeric materials. Incertain embodiments, the protective coating may have a thickness ofabout 30 nm or less, 20 nm or less or 10 nm or less. Exemplary methodsfor forming the protective coating include atomic layer deposition (ALD)and molecular layer deposition (MLD). These techniques allow depositionof one atomic or molecular layer at a time and may form a conformalcoating. In some embodiments, the protective coating may have a smoothersurface than the underlying polymeric coating, which results in themicrostructures having a smoother topography. Alternatively, theprotective coating may be applied to the polymeric coating before theformation of the microstructures.

The lead wire, including the polymeric coating having microstructures,and optionally including the protective coating, can be positionedwithin a lead body (block 152). In certain embodiments, the lead wire ispositioned in a lumen running axially through the lead body (e.g., fromthe distal end to the proximal end of the lead body). The polymericcoating is located between the inner surface of the lead body and theouter surface of the lead wire and may reduce friction between and/orwear from contact between the lead body and the lead wire.

A lubricant may optionally be dispensed between the lead wire and thelead body (item 154). The microstructures formed on the lead wire mayassist in maintaining the lubricant dispersed along the length of thelead wire. In certain embodiments, the lubricant may further reducefriction between the inner surface of the lead body and the lead wire,and may reduce wear or abrasion on the inner surface of the lead bodyfrom the lead wire.

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of the presentinvention. For example, while the embodiments described above refer toparticular features, the scope of this invention also includesembodiments having different combinations of features and embodimentsthat do not include all of the described features. Accordingly, thescope of the present invention is intended to embrace all suchalternatives, modifications, and variations as fall within the scope ofthe claims, together with all equivalents thereof.

We claim:
 1. An implantable medical device comprising: a lead bodyhaving a distal end and a proximal end; a lumen extending through thelead body from the distal end to the proximal end; at least one leadwire extending through the lumen from the distal end to the proximalend, the lead wire having an outer surface; and a polymeric coating onat least a portion of the outer surface of the lead wire, wherein thecoating comprises a plurality of flexible microstructures extendingoutwardly from a surface of the polymeric coating.
 2. The implantablemedical device of claim 1, and further comprising: a second lumenextending through the lead body; at least one second lead wire extendingthrough the second lumen; and a second polymeric coating on at least aportion of the outer surface of the second lead wire, wherein the secondpolymeric coating comprises a plurality of flexible microstructuresextending outwardly from a surface of the second polymeric coating 3.The implantable medical device of claim 1, wherein the flexiblemicrostructures include a first end and a second end, and the distancefrom the first end to the second end is from 5 micrometers to 100micrometers.
 4. The implantable medical device of claim 1, wherein thecoating includes at least one member selected from the group consistingof ethylene tetrafluoroethylene (ETFE) and polyethylene terephthalate(PET).
 5. The implantable medical device of claim 1, and furthercomprising a protective coating on at least a portion of the flexiblemicrostructures.
 6. The implantable medical device of claim 5, whereinthe protective coating has a thickness of 3 nanometers to 30 nanometers.7. The implantable medical device of claim 5, wherein the protectivecoating has a higher modulus of elasticity than the polymeric coating.8. The implantable medical device of claim 1, and further comprising alubricant between at least a portion of an inner surface of the leadbody and at least a portion of the microstructures.
 9. An implantablemedical device comprising: a lead body having a distal end and aproximal end and including at least one lumen and at least one innersurface extending from the distal end to the proximal end; at least onelead wire extending through the at least one lumen and having an outersurface; and a polymeric coating disposed on at least a portion of theouter surface of the at least one lead wire, wherein the polymericcoating comprises a plurality of flexible microstructures that extendoutwardly from a surface of the polymeric coating and have at least onepoint of contact with the inner surface of the lead body.
 10. Theimplantable medical device of claim 9, wherein the microstructures areintegral with the polymeric coating.
 11. The implantable medical deviceof claim 9, wherein the microstructures can bend at least 0.0015radians.
 12. The implantable medical device of claim 9, wherein themicrostructures have a minimum diameter and a length that is at leasttwice the minimum diameter.
 13. A method of forming an implantablemedical device, the method comprising: forming a polymeric coating on anouter surface of a lead wire; and treating the coating to form aplurality of flexible microstructures extending outward from a surfaceof the coating.
 14. The method of claim 13, wherein treating the coatingincludes laser treating the coating.
 15. The method of claim 13, whereintreating the coating includes treating the coating with carbon dioxide.16. The method of claim 13, wherein forming the polymeric coatingincludes forming a polymeric coating having a thickness from 5micrometers to 100 micrometers.
 17. The method of claim 13, and furthercomprising applying a protective coating on at least a portion of theflexible microstructure.
 18. The method of claim 17, wherein applying aprotective coating comprises: applying at least one layer including apolymeric material; and applying at least one layer including a ceramicmaterial, wherein the layer including the ceramic material has athickness of about 30 nanometers or less.
 19. The method of claim 13,and further comprising positioning the lead wire having the plurality ofmicrostructures within a lumen of a lead body, wherein the polymercoating has a higher modulus of elasticity than the lead body.
 20. Themethod of claim 19, and further comprising dispensing a lubricantbetween the microstructures and the lead body.